Objective To study and compare the effect of end-to-end and end-to-side neurorrhaphy between the reci pient’s musculocutaneous nerve and the donor’s ulnar nerve, and to observe the regeneration of peri pheral nerve and muscle refection. Methods Sixty male SD rats (weighing 200-250 g) were randomized into 2 groups (n=30 per group), and made the musculocutaneous nerve injury model. In group A, the donor’s nerve was transected for end-to-end neurorrhaphy.In group B, an epineurial window was exposed and the distal end of the muscle branch of musculocutaneous nerve was sutured to the side of the ulnar nerve. Electromyography was performed, biceps wet weight ratio, muscle fiber cross-sectional area, and count of myel inated nerve fiber (CMF) were measured at 4 and 12 weeks postoperatively. The behavior changes of the rats were observed. Results At 4 weeks, the nerve conduction velocity (NCV) and the latency ampl itude (AMP) of group A were significantly higher than those of group B (P lt; 0.05); at 12 weeks, there was no significant difference in the NCV and AMP between groups A and B (P gt; 0.05). At 4 and 8 weeks, there was no significant difference in biceps wet weight ratio and muscle fiber cross-sectional area between groups A and B (P gt; 0.05). At 4 weeks, the CMF was 230.15 ± 60.25 in group A and 160.73 ± 48.77 in group B, showing significant difference (P lt; 0.05); at 12 weeks, it was 380.26 ± 10.01 in group A and 355.63 ± 28.51 in group B, showing no significant difference (P gt; 0.05). Conclusion Both end-to-end and end-to-side neurorrhaphy have consistent long-term effect in repair of brachial plexus upper trunk injury.